Electrochemical sensing of sodium ions present in bovine serum using 4-tert-butylcalix[4]arene as a receptor†

The concentration of sodium ions can cause severe imbalances (high pressure on blood vessels, swelling of the muscular tissues, and misfunctioning of the whole nervous system) to the human body when its limits are uncontrolled. Thus, it is necessary to determine the amount of sodium ions present in the blood. Electrochemical sensing is an efficient methodology for detecting lower concentrations of ions even with fewer samples. Calixarenes are one of the supramolecules with a distinctive structure that has a predominant ability to complex with alkali metals. Thus, calixarenes are widely used in the detection of sodium (Na⁺) ions. Herein, 4-tert-butylcalix[4]arene, the simplest and cheapest calixarene, is used to deduce sodium ion concentration by electrochemical sensing approach. The sensitivity of the 4-tert-butylcalix[4]arene/GCE was 0.35269 μA M⁻¹ and the limit of detection was 0.1 ± 0.06 μM, the lowest range of detection reported for sodium ions through differential pulse voltammetry, which is an accurate analysis. This is because calixarenes can interact with sodium ions efficiently through the hydrophilic OH groups at the lower rim of the calixarene structure. The interaction of Na⁺ ions with phenolic OH was confirmed by proton NMR titration against NaOH. 4-tert-Butylcalix[4]arene/GCE is adequately selective against various interfering metal ions, and it can also detect sodium ions with high accuracy (recovery range = 99.25–100.01%) in bovine serums.